<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>案例1</title>
    <style>
      .c1 {
        height: 100px;
        width: 100px;
        background-color: red;
      }
      .c2 {
        height: 100px;
        width: 100px;
        background-color: green;
      }
      .c3 {
        height: 100px;
        width: 100px;
        background-color: red;
      }
    </style>
  </head>
  <body>
    <div class="c1"></div>
    <div class="c2"></div>
    <div class="c3"></div>
  </body>
</html>
